WO2017039384A1

WO2017039384A1 - Method for transmitting and receiving channel state information in wireless communication system and device therefor

Info

Publication number: WO2017039384A1
Application number: PCT/KR2016/009846
Authority: WO
Inventors: 박해욱; 김기준; 김병훈; 박종현
Original assignee: 엘지전자(주)
Priority date: 2015-09-03
Filing date: 2016-09-02
Publication date: 2017-03-09
Also published as: US10575200B2; US20190028913A1

Abstract

According to one aspect of the present invention, a method for reporting channel state information (CSI) of a terminal in a wireless communication system comprises the steps of: receiving, from a base station, CSI-reference signal (RS) resource information on a CSI-RS resource to which a CSI-RS is mapped; receiving the CSI-RS from the base station on the basis of the received CSI-RS resource information, by using at least one antenna port; and reporting, to the base station, the CSI generated on the basis of the received CSI-RS, wherein the CSI-RS resource can be configured by aggregating a plurality of legacy CSI-RS resources.

Description

Method for transmitting and receiving channel state information in wireless communication system and apparatus therefor

The present invention relates to a wireless communication system, and more particularly, to a method for transmitting and receiving channel state information and a device for supporting the same.

Mobile communication systems have been developed to provide voice services while ensuring user activity. However, the mobile communication system has expanded not only voice but also data service.As a result of the explosive increase in traffic, a shortage of resources and users are demanding higher speed services, a more advanced mobile communication system is required. have.

The requirements of the next generation of mobile communication systems will be able to accommodate the explosive data traffic, dramatically increase the data rate per user, greatly increase the number of connected devices, very low end-to-end latency, and high energy efficiency. It should be possible. Dual connectivity, Massive Multiple Input Multiple Output (MIMO), In-band Full Duplex, Non-Orthogonal Multiple Access (NOMA), Super Various technologies such as wideband support and device networking have been studied.

An object of the present invention is to propose a method for transmitting and receiving channel state information (CSI).

It is also an object of the present invention to propose an efficient CSI-RS pattern capable of full power transmission.

The technical problems to be achieved in the present invention are not limited to the technical problems mentioned above, and other technical problems not mentioned above will be clearly understood by those skilled in the art from the following description. Could be.

An aspect of the present invention is a method for reporting channel state information (CSI) of a terminal in a wireless communication system, the channel state information-reference signal (CSI-RS) Receiving CSI-RS resource information about a CSI-RS resource to which is mapped from a base station; Receiving the CSI-RS from the base station using at least one antenna port based on the received CSI-RS resource information; And reporting the CSI generated based on the received CSI-RS to the base station. Including, but the CSI-RS resources may be configured by a plurality of legacy CSI-RS resources are aggregated (aggregated).

In addition, when the CSI-RS is received from the base station through a predetermined number of antenna ports, the CSI-RS resources are received through the fewer number of antenna ports than the predetermined number in the legacy system by the legacy CSI-RS. It may consist of merging of resources.

In addition, when the CSI-RS is received through the eight antenna ports from the base station, the resource of the CSI-RS is the legacy CSI-RS to which the CSI-RS received through the four antenna ports in the legacy system is mapped. It may consist of two resources, or the legacy CSI-RS resources to which the CSI-RS received through the two antenna ports in the legacy system is mapped.

In addition, when the eight antenna ports are grouped by four antenna ports to configure two antenna port groups, the CSI-RS received through the eight antenna ports is frequency division multiplexed for each antenna port group. And coded multiplexed for each antenna port in the antenna port group.

In addition, the CSI-RS resource for each of the two antenna port groups may have two or four Orthogonal Frequency Division Multiplexing (OFDM) symbol lengths in the time domain.

Further, when the CSI-RS is received through the four antenna ports from the base station, the resources of the CSI-RS are mapped to the legacy CSI-RS to which the CSI-RS received through the two antenna ports in the legacy system is mapped. It can consist of two resources.

In addition, when the four antenna ports are grouped by two antenna ports to configure two antenna port groups, the CSI-RS received through the four antenna ports is frequency division multiplexed for each antenna port group. And coded multiplexed for each antenna port in the antenna port group.

In addition, the two legacy CSI-RS resources may be continuously located in the frequency domain or may be located in different OFDM symbols in the time domain.

In addition, an antenna port number mapped to each RE (Resource Element) included in the CSI-RS resource may be determined based on the carrier index, the OFDM symbol index, and the CDM order of each antenna port of the RE.

In addition, when a plurality of CSI-RS resources for the same number of antenna ports are set, priority may be set higher as the frequency interval between resource elements included in each CSI-RS resource is smaller.

In addition, the CSI-RS resource information may be higher layer signaled and transmitted to the terminal.

In addition, the CSI-RS resource information, the additional identifier indicating the number of antenna ports of the information of the merged plurality of legacy CSI-RS resources and the CSI-RS resources of the plurality of merged legacy CSI-RS resources It may include.

In addition, the resources of the CSI-RS may be included in the same subframe.

In addition, a terminal for transmitting channel state information (CSI) in a wireless communication system according to another embodiment of the present invention, comprising: a radio frequency (RF) unit for transmitting and receiving a radio signal; And a processor controlling the RF unit; The processor may include receiving CSI-RS resource information about a CSI-RS resource to which channel state information-reference signal (CSI-RS) is mapped from a base station, and receiving the received CSI-RS resource. Receive the CSI-RS from the base station using at least one antenna port based on the information, and reporting the CSI generated based on the received CSI-RS to the base station, the CSI-RS resources May be configured by a plurality of legacy CSI-RS resources aggregated.

According to an embodiment of the present invention, the terminal may smoothly derive and feed back the CSI to the base station.

In addition, when using the CSI-RS pattern according to an embodiment of the present invention, the maximum power transmission is possible.

In addition, when using the CSI-RS pattern according to an embodiment of the present invention, since the CSI-RS pattern of the legacy system is reused, it is possible to derive / use a new and efficient CSI-RS pattern without significantly changing the legacy system. Has This also has the effect that compatibility with new systems and legacy systems can be maintained.

The effects obtainable in the present invention are not limited to the above-mentioned effects, and other effects not mentioned will be clearly understood by those skilled in the art from the following description. .

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, included as part of the detailed description in order to provide a thorough understanding of the present invention, provide embodiments of the present invention and together with the description, describe the technical features of the present invention.

1 illustrates a structure of a radio frame in a wireless communication system to which the present invention can be applied.

2 is a diagram illustrating a resource grid for one downlink slot in a wireless communication system to which the present invention can be applied.

3 shows a structure of a downlink subframe in a wireless communication system to which the present invention can be applied.

4 shows a structure of an uplink subframe in a wireless communication system to which the present invention can be applied.

5 is a configuration diagram of a general multiple input / output antenna (MIMO) communication system.

6 is a diagram illustrating a channel from a plurality of transmit antennas to one receive antenna.

7 illustrates a reference signal pattern mapped to a downlink resource block pair in a wireless communication system to which the present invention can be applied.

8 is a diagram illustrating a resource to which a reference signal is mapped in a wireless communication system to which the present invention can be applied.

9 is a diagram illustrating a resource to which a reference signal is mapped in a wireless communication system to which the present invention can be applied.

FIG. 10 illustrates a two-dimensional active antenna system having 64 antenna elements in a wireless communication system to which the present invention can be applied.

11 illustrates a system in which a base station or a terminal has a plurality of transmit / receive antennas capable of forming 3D (3-Dimension) beams based on AAS in a wireless communication system to which the present invention can be applied.

12 illustrates a two-dimensional antenna system having cross polarization in a wireless communication system to which the present invention can be applied.

13 illustrates a transceiver unit model in a wireless communication system to which the present invention can be applied.

14 illustrates an 8-port CSI-RS pattern mapped to a subframe to which a normal CP is applied according to an embodiment of the present invention.

FIG. 15 illustrates an 8-port CSI-RS pattern mapped to a subframe to which extended CP is applied according to an embodiment of the present invention.

16 is a flowchart illustrating a CSI reporting method of a terminal according to an embodiment of the present invention.

17 illustrates a block diagram of a wireless communication device according to an embodiment of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. The detailed description, which will be given below with reference to the accompanying drawings, is intended to explain exemplary embodiments of the present invention and is not intended to represent the only embodiments in which the present invention may be practiced. The following detailed description includes specific details in order to provide a thorough understanding of the present invention. However, one of ordinary skill in the art appreciates that the present invention may be practiced without these specific details.

In some instances, well-known structures and devices may be omitted or shown in block diagram form centering on the core functions of the structures and devices in order to avoid obscuring the concepts of the present invention.

In this specification, a base station has a meaning as a terminal node of a network that directly communicates with a terminal. The specific operation described as performed by the base station in this document may be performed by an upper node of the base station in some cases. That is, it is obvious that various operations performed for communication with a terminal in a network composed of a plurality of network nodes including a base station may be performed by the base station or other network nodes other than the base station. A 'base station (BS)' may be replaced by terms such as a fixed station, a Node B, an evolved-NodeB (eNB), a base transceiver system (BTS), an access point (AP), and the like. . In addition, a 'terminal' may be fixed or mobile, and may include a user equipment (UE), a mobile station (MS), a user terminal (UT), a mobile subscriber station (MSS), a subscriber station (SS), and an AMS ( Advanced Mobile Station (WT), Wireless Terminal (WT), Machine-Type Communication (MTC) Device, Machine-to-Machine (M2M) Device, Device-to-Device (D2D) Device, etc.

Hereinafter, downlink (DL) means communication from a base station to a terminal, and uplink (UL) means communication from a terminal to a base station. In downlink, a transmitter may be part of a base station, and a receiver may be part of a terminal. In uplink, a transmitter may be part of a terminal and a receiver may be part of a base station.

Specific terms used in the following description are provided to help the understanding of the present invention, and the use of such specific terms may be changed to other forms without departing from the technical spirit of the present invention.

The following techniques are code division multiple access (CDMA), frequency division multiple access (FDMA), time division multiple access (TDMA), orthogonal frequency division multiple access (OFDMA), single carrier frequency division multiple access (SC-FDMA), and NOMA It can be used in various radio access systems such as non-orthogonal multiple access. CDMA may be implemented by a radio technology such as universal terrestrial radio access (UTRA) or CDMA2000. TDMA may be implemented with wireless technologies such as global system for mobile communications (GSM) / general packet radio service (GPRS) / enhanced data rates for GSM evolution (EDGE). OFDMA may be implemented in a wireless technology such as IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802-20, evolved UTRA (E-UTRA). UTRA is part of a universal mobile telecommunications system (UMTS). 3rd generation partnership project (3GPP) long term evolution (LTE) is a part of evolved UMTS (E-UMTS) using E-UTRA, and employs OFDMA in downlink and SC-FDMA in uplink. LTE-A (advanced) is the evolution of 3GPP LTE.

Embodiments of the present invention may be supported by standard documents disclosed in at least one of the wireless access systems IEEE 802, 3GPP and 3GPP2. That is, steps or parts which are not described to clearly reveal the technical spirit of the present invention among the embodiments of the present invention may be supported by the above documents. In addition, all terms disclosed in the present document can be described by the above standard document.

For clarity, the following description focuses on 3GPP LTE / LTE-A, but the technical features of the present invention are not limited thereto.

본 발명이 적용될 수 있는 무선 통신 시스템 일반General wireless communication system to which the present invention can be applied

3GPP LTE / LTE-A supports a type 1 radio frame structure applicable to frequency division duplex (FDD) and a type 2 radio frame structure applicable to time division duplex (TDD).

In FIG. 1, the size of the radio frame in the time domain is expressed as a multiple of a time unit of T_s = 1 / (15000 * 2048). Downlink and uplink transmission consists of a radio frame having a period of T_f = 307200 * T_s = 10ms.

1A illustrates the structure of a type 1 radio frame. Type 1 radio frames may be applied to both full duplex and half duplex FDD.

A radio frame consists of 10 subframes. One radio frame is composed of 20 slots having a length of T_slot = 15360 * T_s = 0.5ms, and each slot is assigned an index of 0 to 19. One subframe consists of two consecutive slots in the time domain, and subframe i consists of slot 2i and slot 2i + 1. The time taken to transmit one subframe is called a transmission time interval (TTI). For example, one subframe may have a length of 1 ms and one slot may have a length of 0.5 ms.

In FDD, uplink transmission and downlink transmission are distinguished in the frequency domain. While there is no restriction on full-duplex FDD, the terminal cannot simultaneously transmit and receive in half-duplex FDD operation.

One slot includes a plurality of orthogonal frequency division multiplexing (OFDM) symbols in the time domain and a plurality of resource blocks (RBs) in the frequency domain. Since 3GPP LTE uses OFDMA in downlink, the OFDM symbol is for representing one symbol period. The OFDM symbol may be referred to as one SC-FDMA symbol or symbol period. A resource block is a resource allocation unit and includes a plurality of consecutive subcarriers in one slot.

FIG. 1B illustrates a frame structure type 2. FIG.

Type 2 radio frames consist of two half frames each 153600 * T_s = 5 ms in length. Each half frame consists of five subframes of 30720 * T_s = 1ms in length.

In a type 2 frame structure of a TDD system, an uplink-downlink configuration is a rule indicating whether uplink and downlink are allocated (or reserved) for all subframes.

Table 1 shows an uplink-downlink configuration.

Referring to Table 1, for each subframe of a radio frame, 'D' represents a subframe for downlink transmission, 'U' represents a subframe for uplink transmission, and 'S' represents a downlink pilot. A special subframe consisting of three fields: a time slot, a guard period (GP), and an uplink pilot time slot (UpPTS).

DwPTS is used for initial cell search, synchronization or channel estimation at the terminal. UpPTS is used for channel estimation at the base station and synchronization of uplink transmission of the terminal. GP is a section for removing interference caused in the uplink due to the multipath delay of the downlink signal between the uplink and the downlink.

Each subframe i is composed of slots 2i and slots 2i + 1 each having a length of T_slot = 15360 * T_s = 0.5ms.

The uplink-downlink configuration can be classified into seven types, and the location and / or number of downlink subframes, special subframes, and uplink subframes are different for each configuration.

The time point when the downlink is changed from the uplink or the time point when the uplink is switched to the downlink is called a switching point. Switch-point periodicity refers to a period in which an uplink subframe and a downlink subframe are repeatedly switched in the same manner, and both 5ms or 10ms are supported. In case of having a period of 5ms downlink-uplink switching time, the special subframe S exists every half-frame, and in case of having a period of 5ms downlink-uplink switching time, it exists only in the first half-frame.

In all configurations,

subframes

0 and 5 and DwPTS are sections for downlink transmission only. The subframe immediately following the UpPTS and the subframe subframe is always an interval for uplink transmission.

The uplink-downlink configuration may be known to both the base station and the terminal as system information. When the uplink-downlink configuration information is changed, the base station may notify the terminal of the change of the uplink-downlink allocation state of the radio frame by transmitting only an index of the configuration information. In addition, the configuration information is a kind of downlink control information, which may be transmitted through a physical downlink control channel (PDCCH) like other scheduling information, and is commonly transmitted to all terminals in a cell through a broadcast channel as broadcast information. May be

Table 2 shows the configuration of the special subframe (length of DwPTS / GP / UpPTS).

The structure of a radio frame according to the example of FIG. 1 is just one example, and the number of subcarriers included in the radio frame or the number of slots included in the subframe and the number of OFDM symbols included in the slot may vary. Can be.

Referring to FIG. 2, one downlink slot includes a plurality of OFDM symbols in the time domain. Here, one downlink slot includes seven OFDM symbols, and one resource block includes 12 subcarriers in a frequency domain, but is not limited thereto.

Each element on the resource grid is a resource element, and one resource block (RB) includes 12 × 7 resource elements. The number N ^ DL of resource blocks included in the downlink slot depends on the downlink transmission bandwidth.

The structure of the uplink slot may be the same as the structure of the downlink slot.

Referring to FIG. 3, up to three OFDM symbols in the first slot in a subframe are control regions to which control channels are allocated, and the remaining OFDM symbols are data regions to which PDSCH (Physical Downlink Shared Channel) is allocated. data region). An example of a downlink control channel used in 3GPP LTE includes a physical control format indicator channel (PCFICH), a physical downlink control channel (PDCCH), a physical hybrid-ARQ indicator channel (PHICH), and the like.

The PCFICH is transmitted in the first OFDM symbol of a subframe and carries information about the number of OFDM symbols (ie, the size of the control region) used for transmission of control channels within the subframe. The PHICH is a response channel for the uplink and carries an ACK (Acknowledgement) / NACK (Not-Acknowledgement) signal for a hybrid automatic repeat request (HARQ). Control information transmitted through the PDCCH is called downlink control information (DCI). The downlink control information includes uplink resource allocation information, downlink resource allocation information or an uplink transmission (Tx) power control command for a certain terminal group.

The PDCCH is a resource allocation and transmission format of DL-SCH (Downlink Shared Channel) (also referred to as a downlink grant), resource allocation information of UL-SCH (Uplink Shared Channel) (also called an uplink grant), and PCH ( Paging information in paging channel, system information in DL-SCH, resource allocation for upper-layer control message such as random access response transmitted in PDSCH, arbitrary terminal A set of transmission power control commands for individual terminals in a group, activation of voice over IP (VoIP), and the like may be carried. The plurality of PDCCHs may be transmitted in the control region, and the terminal may monitor the plurality of PDCCHs. The PDCCH consists of a set of one or a plurality of consecutive CCEs. CCE is a logical allocation unit used to provide a PDCCH with a coding rate according to the state of a radio channel. The CCE corresponds to a plurality of resource element groups. The format of the PDCCH and the number of available bits of the PDCCH are determined according to the association between the number of CCEs and the coding rate provided by the CCEs.

The base station determines the PDCCH format according to the DCI to be transmitted to the terminal, and attaches a CRC (Cyclic Redundancy Check) to the control information. The CRC is masked with a unique identifier (referred to as RNTI (Radio Network Temporary Identifier)) according to the owner or purpose of the PDCCH. If the PDCCH for a specific terminal, a unique identifier of the terminal, for example, a C-RNTI (Cell-RNTI) may be masked to the CRC. Alternatively, if the PDCCH is for a paging message, a paging indication identifier, for example, P-RNTI (P-RNTI) may be masked to the CRC. If the system information, more specifically, the PDCCH for the system information block (SIB), the system information identifier and the system information RNTI (SI-RNTI) may be masked to the CRC. In order to indicate a random access response that is a response to the transmission of the random access preamble of the UE, a random access-RNTI (RA-RNTI) may be masked to the CRC.

Referring to FIG. 4, an uplink subframe may be divided into a control region and a data region in the frequency domain. A physical uplink control channel (PUCCH) carrying uplink control information is allocated to the control region. The data region is allocated a Physical Uplink Shared Channel (PUSCH) that carries user data. In order to maintain a single carrier characteristic, one UE does not simultaneously transmit a PUCCH and a PUSCH.

A PUCCH for one UE is allocated a resource block (RB) pair in a subframe. RBs belonging to the RB pair occupy different subcarriers in each of the two slots. This RB pair allocated to the PUCCH is said to be frequency hopping at the slot boundary (slot boundary).

MIMOMIMO (Multi-Input Multi-Output)(Multi-Input Multi-Output)

MIMO technology generally uses multiple transmit (Tx) antennas and multiple receive (Rx) antennas away from the ones that generally use one transmit antenna and one receive antenna. In other words, the MIMO technology is a technique for increasing capacity or individualizing performance by using multiple input / output antennas at a transmitting end or a receiving end of a wireless communication system. Hereinafter, 'MIMO' will be referred to as a 'multi-input / output antenna'.

More specifically, the multi-input / output antenna technology does not rely on one antenna path to receive one total message, but collects a plurality of pieces of data received through several antennas to complete complete data. As a result, multiple input / output antenna technology can increase the data rate within a specific system range, and can also increase the system range through a specific data rate.

Next-generation mobile communication requires much higher data rates than conventional mobile communication, so efficient multi-input / output antenna technology is required. In such a situation, MIMO communication technology is the next generation mobile communication technology that can be widely used in mobile communication terminals and repeaters, and attracts attention as a technology that can overcome the transmission limit of other mobile communication depending on the limit situation due to the expansion of data communication. have.

Meanwhile, among various transmission efficiency improvement technologies currently being studied, multiple input / output antenna (MIMO) technology has received the most attention as a method for dramatically improving communication capacity and transmission / reception performance without additional frequency allocation or power increase.

Referring to FIG. 5, when the number of transmitting antennas is increased to N_T and the number of receiving antennas is increased to N_R at the same time, the theoretical channel transmission capacity is proportional to the number of antennas unlike the case where a plurality of antennas are used only in a transmitter or a receiver. As a result, it is possible to improve the transfer rate and to significantly improve the frequency efficiency. In this case, the transmission rate according to the increase in the channel transmission capacity may theoretically increase as the maximum rate R_o multiplied by the following rate increase rate R_i when using one antenna.

That is, for example, in a MIMO communication system using four transmit antennas and four receive antennas, a transmission rate four times higher than a single antenna system may be theoretically obtained.

The technique of the multiple input / output antennas improves transmission rate by simultaneously transmitting a plurality of data symbols by using a spatial diversity scheme that improves transmission reliability by using symbols passing through various channel paths and by using a plurality of transmit antennas. It can be divided into spatial multiplexing method. In addition, researches on how to appropriately combine these two methods to obtain the advantages of each are being studied in recent years.

The following is a more detailed description of each method.

First, in the case of the spatial diversity scheme, there is a space-time block code sequence and a space-time trellis code sequence system that simultaneously uses diversity gain and coding gain. In general, the bit error rate improvement performance and the code generation freedom are excellent in the trellis code method, but the operation complexity is simple in the space-time block code. Such a spatial diversity gain can be obtained by an amount corresponding to the product N_T × N_R of the number of transmit antennas N_T and the number of receive antennas N_R.

Secondly, the spatial multiplexing technique is a method of transmitting different data strings at each transmitting antenna, and at the receiver, mutual interference occurs between data transmitted simultaneously from the transmitter. The receiver removes this interference using an appropriate signal processing technique and receives it. The noise cancellation schemes used here include: maximum likelihood detection (MLD) receivers, zero-forcing (ZF) receivers, minimum mean square error (MMSE) receivers, Diagonal-Bell Laboratories Layered Space-Time (D-BLAST), and V-BLAST (Vertical-Bell Laboratories Layered Space-Time). In particular, when the transmitting end can know the channel information, a SVD (singular value decomposition) method can be used.

Third, there is a combined technique of spatial diversity and spatial multiplexing. If only the spatial diversity gain is obtained, the performance improvement gain is gradually saturated as the diversity order is increased, and if only the spatial multiplexing gain is taken, transmission reliability is deteriorated in the wireless channel. In order to solve this problem, methods for obtaining both gains have been studied. Among them, there are a space-time block code (Double-STTD) and a space-time BICM (STBICM).

In order to describe the communication method in the multi-input / output antenna system as described above in more detail, mathematical modeling may be expressed as follows.

First, it is assumed that there are N_T transmit antennas and N_R receive antennas as shown in FIG. 5.

First, referring to the transmission signal, if there are N_T transmission antennas as described above, the maximum transmittable information is N_T, so this may be represented by the following vector.

On the other hand, the transmission power can be different in each of the transmission information s_1, s_2, ..., s_N_T, and if each transmission power is P_1, P_2, ..., P_N_T, the transmission information is adjusted transmission power Can be represented by the following vector:

In addition, the transmission information in which the transmission power of Equation 3 is adjusted may be represented as a diagonal matrix P of the transmission power as follows.

Meanwhile, the information vector of which the transmission power of Equation 4 is adjusted is then multiplied by the weight matrix W to form N_T transmission signals x_1, x_2, ..., x_N_T which are actually transmitted. Here, the weight matrix plays a role of appropriately distributing transmission information to each antenna according to a transmission channel situation. Such transmission signals x_1, x_2, ..., x_N_T can be expressed as follows using a vector x.

Here, w_ij represents a weight between the i th transmit antenna and the j th transmission information, and W represents this in a matrix. Such a matrix W is called a weight matrix or a precoding matrix.

On the other hand, the above-described transmission signal (x) can be considered divided into the case of using the spatial diversity and the case of using the spatial multiplexing.

In the case of using spatial multiplexing, since different signals are multiplexed and sent, the elements of the information vector s all have different values, while using spatial diversity causes the same signal to be sent through multiple channel paths. Therefore, the elements of the information vector s all have the same value.

Of course, a method of mixing spatial multiplexing and spatial diversity is also conceivable. That is, for example, the same signal may be transmitted using spatial diversity through three transmission antennas, and the rest may be considered to be spatially multiplexed to transmit different signals.

Next, when there are N_R reception antennas, the reception signals are represented by the vectors y, respectively, of the reception signals y_1, y_2, ..., y_N_R of each antenna as follows.

Meanwhile, when modeling a channel in a multiple input / output antenna communication system, each channel may be classified according to a transmit / receive antenna index, and a channel passing through the receive antenna i from the transmit antenna j will be denoted as h_ij. Note that the order of the index of h_ij is that of the receiving antenna index first and that of the transmitting antenna is later.

These channels can be grouped together and displayed in vector and matrix form. An example of the vector display is described as follows.

As shown in FIG. 6, a channel arriving from a total of N_T transmit antennas to a reception antenna i may be expressed as follows.

In addition, when all the channels passing through the N_R receiving antennas from the N_T transmitting antennas through the matrix representation as shown in Equation 7 can be expressed as follows.

On the other hand, since the real channel is added with white noise (AWGN) after passing through the channel matrix H as described above, white noise n_1, n_2, ..., n_N_R added to each of the N_R receiving antennas is expressed as a vector. Is as follows.

Through the modeling of the transmission signal, the reception signal, the channel, and the white noise as described above, each of the multiple input / output antenna communication systems may be represented through the following relationship.

On the other hand, the number of rows and columns of the channel matrix H indicating the state of the channel is determined by the number of transmit and receive antennas. As described above, in the channel matrix H, the number of rows is equal to the number of receiving antennas N_R, and the number of columns is equal to the number of transmitting antennas N_T. In other words, the channel matrix H becomes an N_R × N_T matrix.

In general, the rank of a matrix is defined as the minimum number of rows or columns that are independent of each other. Thus, the rank of the matrix cannot be greater than the number of rows or columns. For example, the rank (H) of the channel matrix H is limited as follows.

In addition, when the matrix is subjected to eigen value decomposition, the rank may be defined as the number of nonzero eigenvalues among eigen values. Similarly, the rank can be defined as the number of non-zero singular values when SVD (singular value decomposition). Therefore, the physical meaning of rank in the channel matrix is the maximum number that can send different information in a given channel.

In the present specification, 'rank' for MIMO transmission indicates the number of paths that can independently transmit a signal at a specific time point and a specific frequency resource, and 'number of layers' indicates transmission on each path. The number of signal streams to be represented. In general, since the transmitting end transmits the number of layers corresponding to the number of ranks used for signal transmission, unless otherwise specified, the rank has the same meaning as the number of layers.

참조 신호(Reference signal ( RSRS : Reference Signal): Reference Signal)

Since data is transmitted over a wireless channel in a wireless communication system, the signal may be distorted during transmission. In order to correctly receive the distorted signal at the receiving end, the distortion of the received signal must be corrected using the channel information. In order to detect channel information, a signal transmission method known to both a transmitting side and a receiving side and a method of detecting channel information using a distorted degree when a signal is transmitted through a channel are mainly used. The above-mentioned signal is called a pilot signal or a reference signal (RS).

In addition, in recent years, when transmitting a packet in most mobile communication systems, a method of improving transmission / reception data efficiency by adopting a multiplexing antenna and a multiplexing antenna is avoided from using one transmitting antenna and one receiving antenna. use. When transmitting and receiving data using multiple input / output antennas, a channel state between a transmitting antenna and a receiving antenna must be detected in order to receive a signal accurately. Therefore, each transmit antenna must have a separate reference signal.

In a mobile communication system, RS can be classified into two types according to its purpose. There is an RS for obtaining channel state information and an RS used for data demodulation. Since the former is intended for the UE to acquire channel state information on the downlink, it should be transmitted over a wide band, and a UE that does not receive downlink data in a specific subframe should be able to receive and measure its RS. It is also used for radio resource management (RRM) measurement such as handover. The latter is an RS that the base station sends along with the corresponding resource when the base station transmits the downlink, and the UE can estimate the channel by receiving the RS, and thus can demodulate the data. This RS should be transmitted in the area where data is transmitted.

The downlink reference signal is one common reference signal (CRS: common RS) for acquiring information on channel states shared by all terminals in a cell, measurement of handover, etc. and a dedicated reference used for data demodulation only for a specific terminal. There is a dedicated RS. Such reference signals may be used to provide information for demodulation and channel measurement. That is, DRS is used only for data demodulation and CRS is used for both purposes of channel information acquisition and data demodulation.

The receiving side (i.e., the terminal) measures the channel state from the CRS and transmits an indicator related to the channel quality such as the channel quality indicator (CQI), precoding matrix index (PMI) and / or rank indicator (RI). Feedback to the base station). CRS is also referred to as cell-specific RS. On the other hand, a reference signal related to feedback of channel state information (CSI) may be defined as CSI-RS.

The DRS may be transmitted through resource elements when data demodulation on the PDSCH is needed. The UE may receive the presence or absence of a DRS through a higher layer and is valid only when a corresponding PDSCH is mapped. The DRS may be referred to as a UE-specific RS or a demodulation RS (DMRS).

Referring to FIG. 7, a downlink resource block pair may be represented by 12 subcarriers in one subframe x frequency domain in a time domain in which a reference signal is mapped. That is, one resource block pair on the time axis (x-axis) has a length of 14 OFDM symbols in the case of normal cyclic prefix (normal CP) (in case of FIG. 7 (a)), and an extended cyclic prefix ( extended CP: Extended Cyclic Prefix) has a length of 12 OFDM symbols (in case of FIG. 7 (b)). The resource elements (REs) described as '0', '1', '2' and '3' in the resource block grid are determined by the CRS of the antenna port indexes '0', '1', '2' and '3', respectively. The location of the resource element described as 'D' means the location of the DRS.

Hereinafter, the CRS will be described in more detail. The CRS is used to estimate a channel of a physical antenna and is distributed in the entire frequency band as a reference signal that can be commonly received to all terminals located in a cell. That is, this CRS is a cell-specific signal and is transmitted every subframe for the wideband. In addition, the CRS may be used for channel quality information (CSI) and data demodulation.

CRS is defined in various formats depending on the antenna arrangement at the transmitting side (base station). In a 3GPP LTE system (eg, Release-8), RS for up to four antenna ports is transmitted according to the number of transmit antennas of a base station. The downlink signal transmitting side has three types of antenna arrangements such as a single transmit antenna, two transmit antennas, and four transmit antennas. For example, if the number of transmitting antennas of the base station is two, CRSs for

antenna ports

0 and 1 are transmitted, and if four, CRSs for antenna ports 0 to 3 are transmitted. When there are four transmitting antennas of the base station, the CRS pattern in one RB is shown in FIG.

If the base station uses a single transmit antenna, the reference signal for the single antenna port is arranged.

When the base station uses two transmit antennas, the reference signals for the two transmit antenna ports are arranged using time division multiplexing (TDM) and / or FDM frequency division multiplexing (FDM) scheme. That is, the reference signals for the two antenna ports are assigned different time resources and / or different frequency resources so that each is distinguished.

In addition, when the base station uses four transmit antennas, reference signals for the four transmit antenna ports are arranged using the TDM and / or FDM scheme. The channel information measured by the receiving side (terminal) of the downlink signal may be transmitted by a single transmit antenna, transmit diversity, closed-loop spatial multiplexing, open-loop spatial multiplexing, or It may be used to demodulate data transmitted using a transmission scheme such as a multi-user MIMO.

When a multiple input / output antenna is supported, when a reference signal is transmitted from a specific antenna port, the reference signal is transmitted to a location of resource elements specified according to a pattern of the reference signal, and the location of resource elements specified for another antenna port. Is not sent to. That is, reference signals between different antennas do not overlap each other.

In more detail with respect to DRS, DRS is used to demodulate data. Precoding weights used for a specific terminal in multiple I / O antenna transmission are used without change to estimate the corresponding channel by combining with the transmission channel transmitted from each transmission antenna when the terminal receives the reference signal.

The 3GPP LTE system (eg, Release-8) supports up to four transmit antennas and a DRS for rank 1 beamforming is defined. The DRS for rank 1 beamforming also indicates a reference signal for antenna port index 5.

LTE system evolution In the advanced LTE-A system, it should be designed to support up to eight transmit antennas in the downlink of the base station. Therefore, RS for up to eight transmit antennas must also be supported. Since the downlink RS in the LTE system defines only RSs for up to four antenna ports, when the base station has four or more up to eight downlink transmit antennas in the LTE-A system, RSs for these antenna ports are additionally defined. Must be designed. RS for up to eight transmit antenna ports must be designed for both the RS for channel measurement and the RS for data demodulation described above.

One of the important considerations in designing the LTE-A system is backward compatibility, i.e., the LTE terminal must work well in the LTE-A system, and the system must also support it. From an RS transmission point of view, an RS for an additional up to eight transmit antenna ports should be additionally defined in the time-frequency domain in which CRS defined in LTE is transmitted every subframe over the entire band. In the LTE-A system, when RS patterns of up to eight transmit antennas are added to all bands in every subframe in the same manner as the CRS of the existing LTE, the RS overhead becomes excessively large.

Therefore, the newly designed RS in LTE-A system is divided into two categories, RS for channel measurement purpose for selecting MCS, PMI, etc. (CSI-RS: Channel State Information-RS, Channel State Indication-RS, etc.) And RS (Data Demodulation-RS) for demodulation of data transmitted through eight transmit antennas.

CSI-RS for the purpose of channel measurement has a feature that is designed for channel measurement-oriented purposes, unlike the conventional CRS is used for data demodulation at the same time as the channel measurement, handover, and the like. Of course, this may also be used for the purpose of measuring handover and the like. Since the CSI-RS is transmitted only for the purpose of obtaining information on the channel state, unlike the CRS, the CSI-RS does not need to be transmitted every subframe. In order to reduce the overhead of the CSI-RS, the CSI-RS is transmitted intermittently on the time axis.

The DM-RS is transmitted to the UE scheduled in the corresponding time-frequency domain for data demodulation. That is, the DM-RS of a specific UE is transmitted only in a region where the UE is scheduled, that is, a time-frequency region in which data is received.

In LTE-A system, up to eight transmit antennas are supported on the downlink of a base station. In the LTE-A system, when the RS for up to 8 transmit antennas are transmitted in every subframe in the same manner as the CRS of the existing LTE, the RS overhead becomes excessively large. Therefore, in the LTE-A system, two RSs are added, separated into CSI-RS for CSI measurement and DM-RS for data demodulation for selecting MCS and PMI. The CSI-RS can be used for purposes such as RRM measurement, but is designed for the purpose of obtaining CSI. Since the CSI-RS is not used for data demodulation, it does not need to be transmitted every subframe. Therefore, in order to reduce the overhead of the CSI-RS, it is intermittently transmitted on the time axis. That is, the CSI-RS may be periodically transmitted with an integer multiple of one subframe or may be transmitted in a specific transmission pattern. At this time, the period or pattern in which the CSI-RS is transmitted may be set by the eNB.

For data demodulation, the DM-RS is transmitted to the UE scheduled in the corresponding time-frequency domain. That is, the DM-RS of a specific UE is transmitted only in a region where the UE is scheduled, that is, a time-frequency region in which data is received.

In order to measure the CSI-RS, the UE must transmit the CSI-RS index of the CSI-RS for each CSI-RS antenna port of the cell to which it belongs, and the CSI-RS resource element (RE) time-frequency position within the transmitted subframe. , And information about the CSI-RS sequence.

In the LTE-A system, the eNB should transmit CSI-RS for up to eight antenna ports, respectively. Resources used for CSI-RS transmission of different antenna ports should be orthogonal to each other. When one eNB transmits CSI-RSs for different antenna ports, these resources may be orthogonally allocated in FDM / TDM manner by mapping CSI-RSs for each antenna port to different REs. Alternatively, the CSI-RSs for different antenna ports may be transmitted in a CDM scheme that maps to orthogonal codes.

When the eNB informs its cell UE of the information about the CSI-RS, it is necessary to first inform the information about the time-frequency to which the CSI-RS for each antenna port is mapped. Specifically, the subframe numbers through which the CSI-RS is transmitted, or the period during which the CSI-RS is transmitted, the subframe offset through which the CSI-RS is transmitted, and the OFDM symbol number where the CSI-RS RE of a specific antenna is transmitted and the frequency interval (spacing), the RE offset or shift value in the frequency axis.

The CSI-RS is transmitted through one, two, four or eight antenna ports. At this time, the antenna ports used are p = 15, p = 15, 16, p = 15, ..., 18, p = 15, ..., 22, respectively. The CSI-RS may be defined only for the subcarrier spacing Δf = 15 kHz.

Within a subframe configured for CSI-RS transmission, the CSI-RS sequence is a complex-valued modulation symbol a_k used as a reference symbol on each antenna port p as shown in Equation 12 below. maps to, l ^ (p)

In Equation 12, k ', l' (where k 'is a subcarrier index in a resource block and l' represents an OFDM symbol index in a slot) and the conditions of n_s are as shown in Table 3 or Table 4 below. It is determined according to the same CSI-RS configuration.

Table 3 illustrates the mapping of (k ', l') from the CSI-RS configuration in the generic CP.

Table 4 illustrates the mapping of (k ', l') from the CSI-RS configuration in the extended CP.

Referring to Table 3 and Table 4, in the transmission of CSI-RS, a maximum of 32 (ICI: inter-cell interference) can be reduced in a multi-cell environment including a heterogeneous network (HetNet) environment. In general CP cases) or up to 28 different configurations are defined.

The CSI-RS configuration is different depending on the number of antenna ports and the CP in the cell, and adjacent cells may have different configurations as much as possible. In addition, the CSI-RS configuration may be divided into a case of applying to both the FDD frame and the TDD frame and the case of applying only to the TDD frame according to the frame structure.

Based on Table 3 and Table 4, (k ', l') and n_s are determined according to the CSI-RS configuration, and time-frequency resources used for CSI-RS transmission are determined according to each CSI-RS antenna port.

8 is a diagram illustrating a resource to which a reference signal is mapped in a wireless communication system to which the present invention can be applied. In particular, FIG. 8 illustrates CSI-RS patterns for a case where 1, 2, 4, or 8 CSI-RS antenna ports are included in a subframe to which a normal CP is applied.

FIG. 8 (a) shows 20 CSI-RS configurations available for CSI-RS transmission by one or two CSI-RS antenna ports, and FIG. 8 (b) shows four CSI-RS antenna ports. 10 shows CSI-RS configurations available for use, and FIG. 8 (c) shows five CSI-RS configurations available for CSI-RS transmission by eight CSI-RS antenna ports.

As such, the radio resource (ie, RE pair) to which the CSI-RS is transmitted is determined according to each CSI-RS configuration.

If one or two antenna ports are configured for CSI-RS transmission for a specific cell, the CSI-RS on the radio resource according to the configured CSI-RS configuration among the 20 CSI-RS configurations shown in FIG. Is sent.

Similarly, if four antenna ports are configured for CSI-RS transmission for a specific cell, CSI-RS is performed on a radio resource according to the configured CSI-RS configuration among the 10 CSI-RS configurations shown in FIG. Is sent. In addition, if eight antenna ports are configured for CSI-RS transmission for a specific cell, CSI-RS is performed on a radio resource according to the CSI-RS configuration among the five CSI-RS configurations shown in FIG. Is sent.

CSI-RS for each antenna port is transmitted by CDM to the same radio resource per two antenna ports (that is, {15,16}, {17,18}, {19,20}, and {21,22}). do. For example, for

antenna ports

15 and 16, the respective CSI-RS complex symbols for

antenna ports

15 and 16 are the same, but different orthogonal codes (e.g., Walsh codes) are multiplied to the same radio resource. The complex symbol of CSI-RS for antenna port 15 is multiplied by [1, 1], and the complex symbol of CSI-RS for antenna port 16 is multiplied by [1 -1] and mapped to the same radio resource. The same applies to the antenna ports {17,18}, {19,20} and {21,22}.

The UE can detect the CSI-RS for a particular antenna port by multiplying the transmitted multiplied code. That is, the multiplied code [1 1] is multiplied to detect the CSI-RS for the antenna port 15, and the multiplied code [1 -1] is multiplied to detect the CSI-RS for the antenna port 16.

8 (a) to (c), when the same CSI-RS configuration index corresponds to a radio resource according to the CSI-RS configuration having a large number of antenna ports, the radio resources according to the CSI-RS configuration having a small number of CSI-RS antenna ports It includes radio resources. For example, in the case of CSI-RS configuration 0, the radio resource for the number of eight antenna ports includes both the radio resource for the number of four antenna ports and the radio resource for the number of one or two antenna ports.

In particular, FIG. 9 illustrates CSI-RS patterns for a case where 1, 2, 4, or 8 CSI-RS antenna ports are included in a subframe to which an extended CP is applied.

FIG. 9 (a) shows 16 CSI-RS configurations available for CSI-RS transmission by one or two CSI-RS antenna ports, and FIG. 8 (b) shows four CSI-RS antenna ports. 8 shows the CSI-RS configurations available for use, and FIG. 8 (c) shows the four CSI-RS configurations available for CSI-RS transmission by eight CSI-RS antenna ports.

If one or two antenna ports are configured for CSI-RS transmission for a specific cell, the CSI-RS on the radio resource according to the configured CSI-RS configuration among the 16 CSI-RS configurations shown in FIG. Is sent.

Similarly, if four antenna ports are configured for CSI-RS transmission for a specific cell, CSI-RS is performed on a radio resource according to the configured CSI-RS configuration among the eight CSI-RS configurations shown in FIG. Is sent. In addition, when eight antenna ports are configured for CSI-RS transmission for a specific cell, CSI-RS is performed on a radio resource according to the CSI-RS configuration among four CSI-RS configurations shown in FIG. 9 (c). A plurality of CSI-RS configurations may be used in one cell. Only non-zero power (NZP) CSI-RS is used with zero or one CSI-RS configuration, and zero power (ZP: zero power) CSI-RS is zero or multiple CSI-RS. Configuration can be used.

For each bit set to 1 in ZP CSI-RS (ZP CSI-RS), a 16-bit bitmap set by the upper layer, the UE corresponds to the four CSI-RS columns of Tables 3 and 4 above. Assume zero transmit power in the REs (except in the case of overlapping with the RE assuming the NZP CSI-RS set by the upper layer). Most Significant Bit (MSB) corresponds to the lowest CSI-RS configuration index, and the next bit in the bitmap corresponds to the next CSI-RS configuration index.

The CSI-RS is transmitted only in a downlink slot that satisfies the condition of (n_s mod 2) in Tables 3 and 4 and a subframe that satisfies the CSI-RS subframe configuration.

For frame structure type 2 (TDD), CSI-RSs are not transmitted in subframes that conflict with special subframe, sync signal (SS), PBCH, or SIB 1 (SystemInformationBlockType1) message transmission or subframes configured for paging message transmission Do not.

In addition, any antenna port that belongs to antenna port set S (S = {15}, S = {15,16}, S = {17,18}, S = {19,20} or S = {21,22}) RE transmitted CSI-RS for is not used for CSI-RS transmission of PDSCH or other antenna port.

Since time-frequency resources used for CSI-RS transmission cannot be used for data transmission, data throughput decreases as CSI-RS overhead increases. In consideration of this, the CSI-RS is not configured to be transmitted every subframe, but is configured to be transmitted at a predetermined transmission period corresponding to a plurality of subframes. In this case, the CSI-RS transmission overhead may be much lower than in the case where the CSI-RS is transmitted every subframe.

Subframe periods (hereinafter, referred to as 'CSI transmission periods') (T_CSI-RS) and subframe offset (Δ_CSI-RS) for CSI-RS transmission are shown in Table 5 below.

Table 5 illustrates a CSI-RS subframe configuration.

Referring to Table 5, the CSI-RS transmission period (T_CSI-RS) and the subframe offset (Δ_CSI-RS) are determined according to the CSI-RS subframe configuration (I_CSI-RS).

The CSI-RS subframe configuration of Table 5 may be set to any one of a 'SubframeConfig' field and a 'zeroTxPowerSubframeConfig' field. The CSI-RS subframe configuration may be set separately for the NZP CSI-RS and the ZP CSI-RS.

The subframe including the CSI-RS satisfies Equation 13 below.

In Equation 13, T_CSI-RS denotes a CSI-RS transmission period, Δ_CSI-RS denotes a subframe offset value, n_f denotes a system frame number, and n_s denotes a slot number.

In the case of a UE in which transmission mode 9 is configured for a serving cell, one UE may configure one CSI-RS resource configuration. In the case of a UE in which transmission mode 10 is configured for a serving cell, the UE may be configured with one or more CSI-RS resource configuration (s).

In the current LTE standard, the CSI-RS configuration is composed of the number of antenna ports (antennaPortsCount), subframe configuration (subframeConfig), resource configuration (resourceConfig), and how many antenna ports the CSI-RS is transmitted on It tells what is the period and offset of the subframe to be transmitted and at which RE location (i.e., frequency and OFDM symbol index) in that subframe.

In more detail, the following parameters for configuring each CSI-RS (resource) are set through higher layer signaling.

CSI-RS resource configuration identifier when transmission mode 10 is set

CSI-RS port count (antennaPortsCount): A parameter indicating the number of antenna ports used for CSI-RS transmission (for example, 1 CSI-RS port, 2 CSI-RS port, 4 CSI-RS port, 8 CSI) -RS port)

CSI-RS configuration (refer to Tables 3 and 4): parameters relating to CSI-RS allocated resource location

CSI-RS subframe configuration (subframeConfig, i.e., I_CSI-RS) (see Table 5): parameters relating to the subframe period and / or offset to which the CSI-RS will be transmitted

When transmit mode 9 is set, transmit power (P_C) for CSI feedback: in relation to the UE's assumption of reference PDSCH transmit power for feedback, the UE derives CSI feedback and scales it in 1 dB steps [-8, 15]. When taking values within the dB range, P_C is assumed to be the ratio of Energy Per Resource Element (EPRE) and CSI-RS EPRE per PDSCH RE.

When transmission mode 10 is set, transmission power (P_C) for CSI feedback for each CSI process. If the CSI subframe sets C_CSI, 0 and C_CSI, 1 are set by the higher layer for the CSI process, P_C is set for each CSI subframe set of the CSI process.

Pseudo-rnadom sequence generator parameter (n_ID)

If transmission mode 10 is set, QCL scrambling identifier (qcl-ScramblingIdentity-r11), CRS port count (crs-PortsCount-r11), MBSFN subframe configuration list (mbsfn-) for QCL (QuasiCo-Located) Type B UE assumption Upper layer parameter ('qcl-CRS-Info-r11') including the SubframeConfigList-r11) parameter

When the CSI feedback value derived by the UE has a value within the range of [-8, 15] dB, P_C is assumed as the ratio of PDSCH EPRE to CSI-RS EPRE. Here, the PDSCH EPRE corresponds to a symbol in which the ratio of PDSCH EPRE to CRS EPRE is ρ_A.

In the same subframe of the serving cell, the CSI-RS and the PMCH are not configured together.

When four CRS antenna ports are configured in frame structure type 2, the UE is a CSI belonging to the [20-31] set (see Table 3) for the normal CP or the [16-27] set for the extended CP (see Table 4). -RS configuration index not set.

The UE uses the CSI-RS antenna port of the CSI-RS resource configuration for delay spread, Doppler spread, Doppler shift, average gain, and average delay. You can assume that you have a QCL relationship.

In UE 10 configured with transmission mode 10 and QCL type B, antenna ports 0-3 corresponding to CSI-RS resource configuration and antenna ports 15-22 corresponding to CSI-RS resource configuration are used for Doppler spread and Doppler shift. can be assumed to be a QCL relationship.

In the case of a UE configured with transmission modes 1-9, one UE may configure one ZP CSI-RS resource configuration for a serving cell. In case of a UE configured with transmission mode 10, one or more ZP CSI-RS resource configurations may be configured for the serving cell.

The following parameters for ZP CSI-RS resource configuration may be configured through higher layer signaling.

ZP CSI-RS Configuration List (zeroTxPowerResourceConfigList) (see Tables 3 and 4): Parameters for zero-power CSI-RS configuration

ZP CSI-RS subframe configuration (eroTxPowerSubframeConfig, i.e. I_CSI-RS) (see Table 5): parameters relating to the subframe period and / or offset in which the zero-power CSI-RS is transmitted

In the same subframe of the serving cell, ZP CSI-RS and PMCH are not set at the same time.

In case of a UE configured with transmission mode 10, one or more CSI-IM (Channel-State Information-Interference Measurement) resource configuration may be set for a serving cell.

The following parameters for configuring each CSI-IM resource may be configured through higher layer signaling.

-ZP CSI-RS configuration (see Table 3 and Table 4)

ZP CSI RS subframe configuration (I_CSI-RS) (see Table 5)

The CSI-IM resource configuration is the same as any one of the configured ZP CSI-RS resource configurations.

The CSI-IM resource and the PMCH in the same subframe of the serving cell are not configured at the same time.

매시브Massive MIMOMIMO (Massive (Massive MIMOMIMO ))

A MIMO system with multiple antennas can be referred to as a Massive MIMO system, and is attracting attention as a means to improve spectral efficiency, energy efficiency, and processing complexity. .

Recently, 3GPP has started to discuss the Massive MIMO system to meet the requirements of the spectrum efficiency of future mobile communication systems. Massive MIMO is also referred to as Full-Dimension MIMO (FD-MIMO).

In the wireless communication system after LTE release (Rel: release-12), the introduction of an active antenna system (AAS) is considered.

Unlike conventional passive antenna systems, in which the amplifier and antenna are separated from each other to adjust the phase and magnitude of the signal, AAS means a system in which each antenna includes an active element such as an amplifier.

AAS eliminates the need for separate cables, connectors, and other hardware to connect amplifiers and antennas with active antennas, thus providing high efficiency in terms of energy and operating costs. In particular, since the AAS supports an electronic beam control scheme for each antenna, it enables advanced MIMO techniques such as forming a precise beam pattern or forming a three-dimensional beam pattern in consideration of the beam direction and beam width.

With the introduction of advanced antenna systems such as AAS, large-scale MIMO structures with multiple input / output antennas and multi-dimensional antenna structures are also considered. For example, unlike a conventional linear antenna array, when a 2-dimensional (2D) antenna array is formed, a 3D beam pattern may be formed by an active antenna of the AAS.

FIG. 10 illustrates a typical two-dimensional (2D) antenna array, and as shown in FIG. 10, a case in which N_t = N_v * N_h antennas has a square shape may be considered. Here, N_h represents the number of antenna columns in the horizontal direction and N_v represents the number of antenna rows in the vertical direction.

With this 2D antenna arrangement, the radio wave can be controlled in both the vertical direction (elevation) and the horizontal direction (azimuth) to control the transmission beam in three-dimensional space. have. This type of wavelength control mechanism may be referred to as three-dimensional beamforming.

FIG. 11 is a diagram illustrating the example described above, and illustrates a 3D MIMO system using a 2D antenna array (ie, 2D-AAS).

When using the 3D beam pattern from the perspective of the transmitting antenna, it is possible to perform quasi-static or dynamic beam forming in the vertical direction as well as the horizontal direction of the beam, and may be considered an application such as vertical sector formation. .

In addition, from the viewpoint of the receiving antenna, when the receiving beam is formed using a large receiving antenna, a signal power increase effect according to the antenna array gain can be expected. Therefore, in the uplink, the base station can receive a signal transmitted from the terminal through a plurality of antennas, the terminal can set its transmission power very low in consideration of the gain of the large receiving antenna to reduce the interference effect. There is an advantage.

In the case of a 2D planar antenna array model considering polarization, it may be illustrated as shown in FIG. 12.

Unlike conventional MIMO systems based on passive antennas, systems based on active antennas gain the gain of the antenna elements by weighting the active elements (e.g. amplifiers) attached (or included) to each antenna element. You can adjust the gain dynamically. Since the radiation pattern depends on the antenna arrangement such as the number of antenna elements, antenna spacing, etc., the antenna system can be modeled at the antenna element level.

An antenna array model such as the example of FIG. 12 may be represented by (M, N, P), which corresponds to a parameter characterizing the antenna array structure.

M is the number of antenna elements with the same polarization in each column (ie in the vertical direction) (ie, the number or angle of antenna elements with + 45 ° slant in each column). Number of antenna elements with a -45 ° slant in the column).

N represents the number of columns in the horizontal direction (ie, the number of antenna elements in the horizontal direction).

P represents the number of dimensions of polarization. As in the case of FIG. 11, P = 2 for cross polarization, and P = 1 for co-polarization.

The antenna port can be mapped to a physical antenna element. An antenna port may be defined by a reference signal associated with the corresponding antenna port. For example, in an LTE system, antenna port 0 may be associated with a cell-specific reference signal (CRS) and antenna port 6 may be associated with a positioning reference signal (PRS).

In one example, there may be a one-to-one mapping between antenna ports and physical antenna elements. This may be the case when a single cross polarization antenna element is used for downlink MIMO or downlink transmit diversity. For example, antenna port 0 may be mapped to one physical antenna element, while antenna port 1 may be mapped to another physical antenna element. In this case, two downlink transmissions exist from the terminal point of view. One is associated with a reference signal for antenna port 0 and the other is associated with a reference signal for antenna port 1.

In another example, a single antenna port can be mapped to multiple physical antenna elements. This may be the case when used for beamforming. Beamforming can direct downlink transmissions to specific terminals by using multiple physical antenna elements. In general, this can be achieved using an antenna array consisting of multiple columns of multiple cross polarization antenna elements. In this case, at the terminal, there is a single downlink transmission generated from a single antenna port. One relates to the CRS for antenna port 0 and the other relates to the CRS for antenna port 1.

In other words, the antenna port represents downlink transmission at the terminal, not actual downlink transmission transmitted from the physical antenna element at the base station.

In another example, multiple antenna ports are used for downlink transmission, but each antenna port may be mapped to multiple physical antenna elements. In this case, the antenna array may be used for downlink MIMO or downlink diversity. For example,

antenna ports

0 and 1 may each map to multiple physical antenna elements. In this case, two downlink transmissions exist from the terminal point of view. One is associated with a reference signal for antenna port 0 and the other is associated with a reference signal for antenna port 1.

In FD-MIMO, MIMO precoding of a data stream may go through antenna port virtualization, transceiver unit (or transceiver unit) (TXRU) virtualization, and antenna element pattern.

Antenna port virtualization allows the stream on the antenna port to be precoded on the TXRU. TXRU virtualization allows the TXRU signal to be precoded on the antenna element. The antenna element pattern may have a directional gain pattern of the signal radiated from the antenna element.

In conventional transceiver modeling, a static one-to-one mapping between antenna ports and TXRU is assumed, and the TXRU virtualization effects are combined into a static (TXRU) antenna pattern that includes both the effects of TXRU virtualization and antenna element patterns.

Antenna port virtualization can be performed in a frequency-selective manner. In LTE, an antenna port is defined with a reference signal (or pilot). For example, for precoded data transmission on the antenna port, the DMRS is transmitted in the same bandwidth as the data signal, and both the DMRS and the data are precoded with the same precoder (or the same TXRU virtualized precoding). For CSI measurement, the CSI-RS is transmitted through multiple antenna ports. In CSI-RS transmission, the precoder characterizing the mapping between the CSI-RS port and TXRU may be designed with a unique matrix so that the UE can estimate the TXRU virtualization precoding matrix for the data precoding vector.

The TXRU virtualization method includes 1D TXRU virtualization and 2D TXRU virtualization, which will be described with reference to the following drawings.

In 1D TXRU virtualization, M_TXRU TXRUs are associated with M antenna elements consisting of a single column antenna array with the same polarization.

In 2D TXRU virtualization, the TXRU model configuration corresponding to the antenna array model configuration (M, N, P) of FIG. 12 may be represented by (M_TXRU, N, P). Here, M_TXRU means the number of TXRUs present in the same column and the same polarization in 2D, and always satisfies M_TXRU ≦ M. That is, the total number of TXRUs is equal to M_TXRU × N × P.

TXRU virtualization model according to the correlation between the antenna element and TXRU as shown in Figure 13 (a) TXRU virtualization model option-1: sub-array partition model (sub-array partition model) and as shown in Figure 13 (b) TXRU virtualization model Option-2: Can be divided into a full-connection model.

Referring to FIG. 13A, in the case of a sub-array partition model, antenna elements are divided into multiple antenna element groups, and each TXRU is connected to one of the groups.

Referring to FIG. 13B, in the full-connection model, signals of multiple TXRUs are combined and delivered to a single antenna element (or an array of antenna elements).

In FIG. 13, q is a transmission signal vector of antenna elements having M equally polarized (co-polarized) in one column. w is the wideband TXRU virtualization weight vector and W is the wideband TXRU virtualization weight matrix. x is a signal vector of M_TXRU TXRUs.

Here, the mapping between the antenna port and the TXRUs may be one-to-one (1-to-1) or one-to-many.

The TXRU-to-element mapping in FIG. 13 shows only one example, and the present invention is not limited thereto, and TXRU and antenna elements may be implemented in various forms from a hardware point of view. The present invention can be equally applied to the mapping between them.

채널 상태 정보 송수신 방법How to send and receive channel status information

The CSI process may be set to two classes, such as CSI reporting class A or CSI reporting class B.

For class A, the UE may report CSI according to W = W1 * W2 codebooks based on {8, 12, 16} CSI-RS antenna ports.

For class B, the UE may report L port CSI assuming one of the following four methods.

Scheme 1: Indicator for beam selection and L port CQI / PMI / RI for the selected beam. The total number of configured ports across all CSI-RS resources in the CSI process is greater than L.

Scheme 2: L port precoder from codebook that jointly reflects both beam selection (s) and phase co-phasing over two polarizations. The total number of configured antenna ports in the CSI process is L.

Scheme 3: Codebook reflecting L port CSI and beam selection for the selected beam. The total number of configured ports across all CSI-RS resources in the CSI process is greater than L.

Option 4: L port CQI / PMI / RI. The total number of ports in the CSI process is L. If CSI measurement limits are supported, they are always set.

Here, beam selection means selection of a subset of antenna ports or selection of CSI-RS resources from a set of resources within a single CSI-RS resource.

In addition, the CSI process is associated with K CSI-RS resource / configuration involving the N_k port for the k-th CSI-RS resource (where K may be equal to or greater than 1).

The maximum total number of CSI-RS ports in one CSI procedure is 16 for CSI reporting class A.

For the RRC configuration of the CSI-RS resource / configuration (especially for CSI reporting class A), one of the following alternatives may be selected.

Alternative 1: A CSI-RS resource / configuration with N_k set to 12 or 16 may be defined. In this case, the index of the CSI-RS configuration may be configured for the CSI procedure when K = 1.

Alternative 2: CSI-RS 12/16 ports may be defined by a combination of CSI-RS resource / configuration consisting of 2/4/8 ports. In this case, K may be greater than one.

Hereinafter, a new CSI-RS pattern / design / configuration (hereinafter, referred to as a “pattern”) that can be applied to the aforementioned CSI reporting class A will be proposed. In particular, the present specification proposes a CSI-RS pattern designed using the legacy CSI-RS pattern / design of the existing system.

14 illustrates an 8-port CSI-RS pattern mapped to a subframe to which a normal CP is applied according to an embodiment of the present invention. For convenience of description, the pattern in which the CSI-RS transmitted through the N antenna ports is mapped to a resource will be referred to as an 'N-port CSI-RS pattern'.

Referring to FIG. 14, the 8-port CSI-RS pattern newly proposed herein may be configured by merging / combining at least some of the legacy 2-port and 4-port CSI-RS patterns. The legacy legacy CSI-RS pattern has a structure in which 2-, 4-, and 8-port CSI-RSs are nested and correspond to a structure capable of full power transmission.

The new 8-port CSI-RS pattern proposed in this specification is also limited to the above-mentioned maximum power transmission pattern in order to increase transmission efficiency. In addition, in order to take full advantage of the CSI-RS pattern defined in the legacy system (that is, to minimize legacy impact), the legacy CSI-RS pattern is mapped to the resource element to which the new 8-port CSI-RS pattern is mapped. Limited to 40 resource units.

1. 8-Port CSI-RS Pattern for Maximum Power Transfer

Legacy 8-Port CSI-RS Pattern

The 8-port CSI-RS pattern capable of maximum power transfer may have a legacy 8-port CSI-RS pattern. That is, it may correspond to the 8-port CSI-RS pattern to which the FDM and the CDM of length 2 are applied. A detailed description thereof is as described above with reference to FIG. 8 (c).

First embodiment

As a new 8-port CSI-RS pattern capable of maximum power transmission, we propose a CSI-RS pattern with FDM and CDM. According to the present embodiment, FDM may be applied to each port group in which a plurality of ports are grouped, and a CDM (CDM length 4) having a length of 4 may be applied to each port in one port group.

For example, the FSI scheme is applied to each port group of {0, 1, 2, 3} and {4, 5, 6, 7}, and the CDM scheme is applied to each port of the same port group. Patterns such as # 1, # 4 and # 5 can be designed. In this case, two port groups (or CSI-RSs transmitted from two port groups) may exist in the same four OFDM symbols, and CDM may be performed by length 4 in the time domain.

That is, CSI-RSs transmitted through different port groups may be classified into FDM schemes, and CSI-RSs transmitted through different ports within the same port group may be classified into CDM schemes. In this case, the weighting vector used in the CDM method may follow Equation 14. That is, CSI-RSs transmitted on different ports in the same port group may be CDM by multiplying different weighting vectors according to Equation (14).

As such, two FDM and CDM port groups {0, 1, 2, 3} and {4, 5, 6, 7} have a total of 8 as shown in CSI-RS patterns # 1, # 4, and # 5 of FIG. -You can configure the CSI-RS pattern of the port.

Second embodiment

As a new 8-port CSI-RS pattern capable of maximum power transmission, we propose a CSI-RS pattern with FDM and CDM. According to the present embodiment, FDM may be applied to each port group in which a plurality of ports are grouped, and CDM of length 4 may be applied to each port in time domain and frequency domain.

For example, the FDM scheme may be applied to each port group of {0, 1, 2, 3} and {4, 5, 6, 7}, and the CDM scheme is applied to each port in the same port group, thereby providing the CSI of FIG. Patterns such as -RS patterns # 2 and # 3 can be designed. In this case, two port groups (or CSI-RSs transmitted from two port groups) may exist in two identical OFDM symbols, and CDM may be performed by length 4 in the time domain.

That is, CSI-RSs transmitted through different port groups may be classified into FDM schemes, and CSI-RSs transmitted through different ports within the same port group may be classified into CDM schemes.

As such, two FDM and CDM port groups ({0, 1, 2, 3} and {4, 5, 6, 7}) have a total of 8-ports as shown in CSI-RS patterns # 2 and # 3 of FIG. CSI-RS pattern can be configured.

2. 4-Port CSI-RS Pattern for Maximum Power Transfer

Legacy 4-port CSI-RS pattern

The 4-port CSI-RS pattern capable of maximum power transfer may have a legacy 4-port CSI-RS pattern. That is, it may correspond to a 4-port CSI-RS pattern to which FDM and a length of 2 CDM are applied. A detailed description thereof is as described above with reference to FIG. 8 (b).

Third embodiment

As a new 4-port CSI-RS pattern capable of maximum power transmission, we propose a CSI-RS pattern with four-length CDM scheme. Similar to the first embodiment, this embodiment performs CDM by length 4 in the time domain for port-specific CSI-RS. For example, in CSI-RS pattern # 1 of FIG. 14, {0, 1}, {2, 3}, {4, 5}, and {6, 7} each represent one new 4-port CSI-RS pattern. Will be configured.

This embodiment may be interpreted as a merged / combined legacy 2-port CSI-RS pattern present (or mapped) in different OFDM symbols.

Fourth embodiment

As a new 4-port CSI-RS pattern capable of maximum power transmission, we propose a CSI-RS pattern with two CDM schemes in the time and frequency domains. Similar to the second embodiment, the present embodiment performs CDMs having a length of 2 in the time domain and a length of 2 in the frequency domain for the CSI-RS for each port. For example, in CSI-RS pattern # 2 of FIG. 14, {0, 1}, {2, 3}, {4, 5}, and {6, 7} each represent one new 4-port CSI-RS pattern. Will be configured.

This embodiment may be interpreted as a merged / combined contiguous legacy 2-port CSI-RS pattern in the frequency domain.

3. 2-Port CSI-RS Pattern for Maximum Power Transmission

Legacy 2-port CSI-RS pattern

The two-port CSI-RS pattern capable of maximum power transmission may include a legacy two-port CSI-RS pattern, and a detailed description thereof is as described above with reference to FIG. 8A.

-Fifth embodiment

A new two-port CSI-RS pattern capable of maximum power transfer, with port 0 and port 1 configured in FDM.

In the above, the new CSI-RS pattern that can satisfy the maximum power transmission has been described. The embodiment of the present invention is not limited to the CSI-RS pattern shown in FIG. 14, and at least some of the above-described / proposed CSI-RS patterns may be combined / expanded to be derived as a new CSI-RS pattern.

Some of the CSI-RS patterns proposed herein are not mapped to resources in the same location as the legacy 2- and 4-port CSI-RS patterns. Therefore, when the new CSI-RS pattern proposed herein coexists with the legacy CSI-RS pattern, a problem may arise in that the new CSI-RS pattern and the legacy CSI-RS pattern may exist in the same resource.

For example, referring to FIG. 8B, in a legacy system, a 4-port CSI-RS may be mapped to two resource element pairs separated by six subcarriers within two identical OFDM symbols and transmitted. In this case, if a new 4-port CSI-RS pattern is mapped / used at positions l = {5, 6} and k = {8, 9} proposed in the fourth embodiment, l = {5 at k = 4. , 6} and k = 3 have a problem that legacy (port) legacy 4-port CSI-RS patterns that are (partly) present / mapped at l = {5, 6} cannot be used. Here, l denotes an OFDM symbol index in the time domain, and 0 to 13 are sequentially allocated from the leftmost to the rightward. Also, k denotes a carrier index in the frequency domain, and 0 to 11 are sequentially allocated from the lowest side to the upper side.

To solve the above problem, the base station is configured to map / use only the legacy 2-port CSI-RS pattern at l = {5,6} at k = 2 and l = {5,6} at k = 3. Can be. That is, the base station may first map a new CSI-RS pattern to the corresponding resource region when at least a portion of the overlap between the resource region to which the legacy CSI-RS pattern is mapped and the resource region to which the new CSI-RS pattern is mappable. .

Or, similar to the legacy 8-port CSI-RS pattern, l = {5, 6}, k = {8, 9} and l = {5, 6}, k = {2, 3} always have two 4 By setting the port CSI-RS to be mapped, only the 4-port CSI-RS according to the fourth embodiment may be mapped / assigned to the corresponding resource location.

The above-described embodiments may be applied to the same / similar to the above-described first to fifth embodiments.

Hereinafter, a rule of numbering CSI-RS ports in a new CSI-RS pattern will be described.

A. First, as shown in FIG. 14, port 0 is assigned to each resource element in the order of CDM, starting with the resource element located at the lowest (or highest) carrier index and the lowest (or higher) OFDM symbol index in a specific port group. , 1, 2, 3 (actually

ports

15, 16, 17, 18, ie, the start of port numbering may not be zero) may be sequentially numbered. In this case, the CDM order may correspond to the order in which the weight vectors W_0 to W_3 in Equation 14 are permutated, or may correspond to the order in which W_0 to W_3 are multiplied by the CSI-RS for each antenna port. For example, in the latter case, W_0 is for the CSI-RS transmitted over port 0, W_1 is for the CSI-RS transmitted over port 1, W_2 is for the CSI-RS transmitted over port 3, and W_3 is for the port. When the CSI-RSs transmitted through 2 are respectively multiplied, the CDM order may be 'port 0 → port 1 → port 3 → port 2'.

B. Next, the port numbering of the port group where the ports 0 to 3 are numbered and the next port group after the FDM may also be performed in the same manner as the port numbering method in the A stage. That is,

ports

4, 5, 6, and 7 (actually) are assigned to each resource element in the order of CDM starting from the resource element located at the lowest (or high) carrier index and the lowest (or high) OFDM symbol index in the corresponding port group. May sequentially number ports 19, 20, 21, and 22).

That is, in the above-described embodiment, the CSI-RS port numbering is performed in CDM → FDM order, but is not limited thereto and may be performed in FDM → CDM order.

In the present specification, a new CSI-RS pattern is proposed among the 40 resource elements that can be allocated for the CSI-RS, which has high flexibility in configuring the CSI-RS pattern and enables maximum power transmission. However, since performance may vary for each CSI-RS pattern, the present disclosure proposes to consider the priority set as follows when selecting / allocating a CSI-RS pattern for a UE.

Performing CDM on resource elements contiguously / continuously located in the frequency domain (or minimizing frequency variation when performing CDM) is advantageous in terms of CDM performance. Accordingly, the smaller the frequency / time domain variation or the smaller the OFDM / carrier spacing among the new CSI-RS patterns proposed herein, the higher the priority pattern may be set. Can be.

For example, in the case of the 8-port CSI-RS patterns of # 1 to # 5 shown in FIG. 14, priority according to CDM performance is determined as follows.

-Pattern # 2> Pattern # 3> Pattern # 4 = Pattern # 1> Pattern # 5

Meanwhile, in terms of increasing network flexibility, the new CSI-RS pattern and the legacy CSI-RS pattern may be used together.

For example, it may be assumed that a specific Cell / TP (Transmission Point) A transmits only the 8-port CSI-RS pattern # 2 proposed in FIG. 14 within one subframe. In this case, the other cell / TP (or the same cell / TP A in addition) has the corresponding 8-port CSI-RS pattern # 2 of the 40 resource elements mapped and the remaining remaining resource elements (or CSI-RS resources). And at least one of the legacy 1-, 2-, 4-, or 8-port CSI-RS patterns may be selected and mapped.

The network may directly instruct the UE through higher layer signaling which CSI-RS pattern the UE should receive and / or derive CSI-RS from. To this end, at least one of the patterns of the first to fifth embodiments described above may be predefined / set.

For example, if two resources (K = 2) are allocated to the UE per one CSI procedure, each of these two resources is 4-port CSI-RS (N_0 = 4) and 8-port CSI-RS (N_1 = Assume that 8) is mapped. In this case, the 4- and 8-port CSI-RS patterns may be composed of conventional legacy 4- and 8-port CSI-RS patterns, respectively, as described above with reference to FIG. 14. It may also consist of a combination / merge of 4-port CSI-RS patterns.

If the 4-port CSI-RS (N_0) pattern consists of a combination / merge of two legacy 2-port CSI-RS patterns, the 8-port CSI-RS (N_1) pattern consists of two legacy 4-port CSI-RS If the combination / merge of the patterns, the base station may signal the CSI-RS pattern to indicate to the terminal as follows.

First legacy 2-port CSI-RS resource / pattern (with flag A)

Second Legacy 2-Port CSI-RS Resource / Pattern (with flag A)

First legacy 4-port CSI-RS resource / pattern (with flag B)

Second Legacy 4-port CSI-RS Resource / Pattern (with flag B)

Here, flag A indicates a 4-port CSI-RS pattern and flag B indicates an 8-port CSI-RS pattern.

That is, the base station provides information about legacy 2-port CSI-RS resources / patterns constituting the 4-port CSI-RS resource / pattern and an additional identifier (flag A) indicating 4-port CSI-RS resources / pattern. Signaling together, the UE can indicate a 4-port CSI-RS resource / pattern. Similarly, the base station may provide information about legacy 4-port CSI-RS resources / patterns constituting the 8-port CSI-RS resource / pattern and an additional identifier indicating flag 8-port CSI-RS resources / pattern (flag B). ) Together with the 8-port CSI-RS resource / pattern can be indicated to the terminal.

In generalizing the above-described example, the base station together signals the CSI-RS pattern consisting of the information of the legacy CSI-RS patterns and the combination / merge of the corresponding legacy CSI-RS patterns, thereby providing CSI-RS resources / You can indicate the pattern.

In addition, the base station may signal information about the legacy CSI-RS resource pattern constituting the CSI-RS resource / pattern in various manners / embodiments, but is not limited to the above-described embodiment.

As described above, the embodiment of the CSI-RS pattern mapped to the subframe to which the normal CP is applied has been described. However, the above-described embodiment is not limited to the subframe to which the normal CP is applied and may be extended to the same / similarly to the subframe to which the extended CP is applied. In this regard it will be described later with respect to FIG.

FIG. 15 illustrates an 8-port CSI-RS pattern mapped to a subframe to which extended CP is applied according to an embodiment of the present invention. In the drawings, the same description as described above with reference to FIG. 14 may be applied.

Referring to FIG. 15, at least some of the 2-port and 4-port CSI-RS patterns mapped to the extended CP-applied subframe in the legacy system are also mapped to the 8-port CSI-RS pattern mapped to the subframe to which the extended CP is applied. It can be configured in the form of merge / combined. In addition, the CSI-RS pattern will also be limited to the above-mentioned maximum power transmission pattern in order to increase transmission efficiency.

As described above with reference to FIG. 14, a CSI-RS pattern to which FDM and CDM are applied may be proposed as a new 8-port CSI-RS pattern capable of maximum power transmission.

As an embodiment, FDM may be applied to each port group in which a plurality of ports are grouped, and a CDM of length 4 may be applied to a time domain for each port. For example, the FSI scheme for each port group of {0, 1, 2, 3} and {4, 5, 6, 7} and the CDM scheme for each port in the same port group are applied to the CSI-RS pattern of FIG. 15. Patterns such as 1, 2 and 7 can be designed. In this case, two port groups (or CSI-RSs transmitted from two port groups) may exist in the same four OFDM symbols, and CDM may be performed by length 4 in the time domain.

In another embodiment, FDM may be applied to each port group in which a plurality of ports are grouped, and a CDM of length 4 may be applied to each port in a time and frequency domain.

For example, the FDM scheme may be applied to each port group of {0, 1, 2, 3} and {4, 5, 6, 7}, and the CDM scheme is applied to each port in the same port group, thereby providing the CSI of FIG. 15. Patterns such as -RS patterns 3 to 6 can be designed. In this case, two port groups (or CSI-RSs transmitted from two port groups) may exist in two identical OFDM symbols, and CDM may be performed by length 4 in the time domain and the frequency domain.

In the case of the extended CP, the description has been made based on the 8-port CSI-RS pattern that can be newly derived. However, the present invention is not limited thereto. Of course, it can be derived into a new CSI-RS pattern (of size).

16 is a flowchart illustrating a CSI reporting method of a terminal according to an embodiment of the present invention. In the flowchart, the above descriptions with respect to FIGS. 14 and 15 may be applied identically or similarly, and overlapping descriptions will be omitted.

Referring to FIG. 16, first, a UE may receive CSI-RS resource information (S1610). Here, the CSI-RS resource information may refer to information about a resource (element) to which the CSI-RS is mapped in the subframe. In this case, the CSI-RS resource, which is the resource to which the CSI-RS is mapped, may be configured by combining a plurality of legacy CSI-RS resources, and may be designed in a pattern capable of maximum power transmission. For example, the CSI-RS pattern of the embodiments described above with reference to FIGS. 14 and 15 may be applied.

Next, the terminal may receive the CSI-RS from the base station using one or more antenna ports based on the received CSI-RS resource information (S1620). Next, the terminal may generate a CSI based on the received CSI-RS and report the generated CSI to the base station (S1630).

In this case, when the CSI-RS is received from the base station through a preset number of antenna ports, the CSI-RS resource may be configured by merging of legacy CSI-RS resources received through a smaller number of antenna ports than the preset number in the legacy system. Can be.

In addition, when the CSI-RS is received through the 8 antenna ports from the base station, the resource of the CSI-RS is composed of two legacy CSI-RS resources mapped to the CSI-RS received through the four antenna ports in the legacy system or In the legacy system, four legacy CSI-RS resources to which CSI-RSs received through two antenna ports are mapped may be configured.

When eight antenna ports are grouped into four antenna ports to configure two antenna port groups, the CSI-RS received through the eight antenna ports is frequency-division multiplexed and transmitted by the antenna port group. Code division multiplexing for each antenna port in a group may be transmitted. In this case, the CSI-RS resources for each of the two antenna port groups may have two or four Orthogonal Frequency Division Multiplexing (OFDM) symbol lengths in the time domain.

Alternatively, when the CSI-RS is received through the four antenna ports from the base station, the resources of the CSI-RS may consist of two legacy CSI-RS resources to which the CSI-RS received through the two antenna ports in the legacy system is mapped. Can be. When four antenna ports are grouped into two antenna ports to configure two antenna port groups, the CSI-RS received through the four antenna ports is transmitted by frequency division multiplexing for each antenna port group. Code division multiplexing for each antenna port in a group may be transmitted. In this case, two legacy CSI-RS resources may be continuously located in the frequency domain or may be located in different OFDM symbols in the time domain.

In addition, an antenna port number mapped to each RE (Resource Element) included in a CSI-RS resource may be determined based on a carrier index, an OFDM symbol index, and a CDM order of antenna ports of the RE.

In addition, the CSI-RS resource information may be higher layer signaled and transmitted to the terminal. In this case, the CSI-RS resource information may include information on a plurality of merged legacy CSI-RS resources and an additional identifier indicating the number of antenna ports of the CSI-RS resources configured by the merged plurality of legacy CSI-RS resources. have.

In addition, resources of the CSI-RS may be included in the same subframe.

본 발명이 적용될 수 있는 장치 일반General apparatus to which the present invention can be applied

Referring to FIG. 17, a wireless communication system includes a base station 1710 and a plurality of terminals 1720 located in an area of a base station 1710.

The base station 1710 includes a processor 1711, a memory 1712, and an RF unit 1713. The processor 1711 implements the functions, processes, and / or methods proposed in FIGS. 1 to 16. Layers of the air interface protocol may be implemented by the processor 1711. The memory 1712 is connected to the processor 1711 and stores various information for driving the processor 1711. The RF unit 1713 is connected to the processor 1711 and transmits and / or receives a radio signal.

The terminal 1720 includes a processor 1721, a memory 1722, and an RF unit 1723. The processor 1721 implements the functions, processes, and / or methods proposed in FIGS. 1 to 16. Layers of the air interface protocol may be implemented by the processor 1721. The memory 1722 is connected to the processor 1721 and stores various information for driving the processor 1721. The RF unit 1723 is connected to the processor 1721 to transmit and / or receive a radio signal.

The

memories

1712 and 1722 may be inside or outside the

processors

1711 and 1721, and may be connected to the

processors

1711 and 1721 by various well-known means. In addition, the base station 1710 and / or the terminal 1720 may have a single antenna or multiple antennas.

The embodiments described above are the components and features of the present invention are combined in a predetermined form. Each component or feature is to be considered optional unless stated otherwise. Each component or feature may be embodied in a form that is not combined with other components or features. It is also possible to combine some of the components and / or features to form an embodiment of the invention. The order of the operations described in the embodiments of the present invention may be changed. Some components or features of one embodiment may be included in another embodiment or may be replaced with corresponding components or features of another embodiment. It is obvious that the claims may be combined to form an embodiment by combining claims that do not have an explicit citation relationship in the claims or as new claims by post-application correction.

Embodiments according to the present invention may be implemented by various means, for example, hardware, firmware, software, or a combination thereof. In the case of a hardware implementation, an embodiment of the present invention may include one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), FPGAs ( field programmable gate arrays), processors, controllers, microcontrollers, microprocessors, and the like.

In the case of implementation by firmware or software, an embodiment of the present invention may be implemented in the form of a module, procedure, function, etc. that performs the functions or operations described above. The software code may be stored in memory and driven by the processor. The memory may be located inside or outside the processor, and may exchange data with the processor by various known means.

It will be apparent to those skilled in the art that the present invention may be embodied in other specific forms without departing from the essential features of the present invention. Accordingly, the above detailed description should not be construed as limiting in all aspects and should be considered as illustrative. The scope of the invention should be determined by reasonable interpretation of the appended claims, and all changes within the equivalent scope of the invention are included in the scope of the invention.

Various aspects for carrying out the invention have been described in the best mode for carrying out the invention.

Although the present invention has been described with reference to the example applied to the 3GPP LTE / LTE-A system, it is possible to apply to various wireless communication systems in addition to the 3GPP LTE / LTE-A system.

Claims

A method for reporting channel state information (CSI) of a terminal in a wireless communication system, the method comprising:

Receiving CSI-RS resource information about a CSI-RS resource to which channel state information-reference signal (CSI-RS) is mapped from a base station;

Receiving the CSI-RS from the base station using at least one antenna port based on the received CSI-RS resource information; And

Reporting the CSI generated based on the received CSI-RS to the base station; Including,

The CSI-RS resource is configured by aggregating a plurality of legacy CSI-RS resources (aggregate), CSI reporting method of the terminal.
The method of claim 1,

When the CSI-RS is received from the base station through a preset number of antenna ports, the CSI-RS resource is

The legacy system CSI reporting method comprising a merge of the legacy CSI-RS resources received through a less than the predetermined number of antenna ports in the legacy system.
The method of claim 2,

When the CSI-RS is received through the eight antenna ports from the base station, the resources of the CSI-RS are:

The legacy system consists of two legacy CSI-RS resources mapped to the CSI-RS received through four antenna ports, or

The CSI reporting method of the UE is composed of the four legacy CSI-RS resources are mapped to the CSI-RS received through the two antenna ports in the legacy system.
The method of claim 3, wherein

When the eight antenna ports are grouped in units of four antenna ports to configure two antenna port groups,

The CSI-RS received through the eight antenna ports is frequency division multiplexed and transmitted by the antenna port group, and code division multiplexed and transmitted by the antenna port in the antenna port group.
The method of claim 4, wherein

The CSI-RS resource for each of the two antenna port groups has two or four Orthogonal Frequency Division Multiplexing (OFDM) symbol lengths in a time domain.
The method of claim 2,

When the CSI-RS is received through the four antenna ports from the base station, the resource of the CSI-RS is the legacy CSI-RS resource 2 to which the CSI-RS received through the two antenna ports in the legacy system is mapped. CSI reporting method of the terminal consisting of a dog.
The method of claim 6,

When the four antenna ports are grouped in units of two antenna ports to configure two antenna port groups,

The CSI-RS received through the four antenna ports is frequency division multiplexed and transmitted by the antenna port group, and code division multiplexed and transmitted by the antenna port in the antenna port group.
The method of claim 6,

The two legacy CSI-RS resources are continuously located in the frequency domain or are located in different OFDM symbols in the time domain, the CSI reporting method of the terminal.
The method of claim 1,

The antenna port number mapped to each resource element (RE) included in the CSI-RS resource is determined based on the carrier index of the RE, the OFDM symbol index, and the CDM order of the antenna ports.
The method of claim 1,

When a plurality of CSI-RS resources for the same number of antenna ports are set, the priority is set higher as the frequency interval between resource elements included in each CSI-RS resources is smaller.
The method of claim 1,

The CSI-RS resource information is higher layer signaled and transmitted to the terminal.
The method of claim 11,

The CSI-RS resource information includes information on the merged plurality of legacy CSI-RS resources and an additional identifier indicating the number of antenna ports of the CSI-RS resources configured by the merged plurality of legacy CSI-RS resources. CSI reporting method of the terminal.
The method of claim 1,

The CSI-RS resource is included in the same subframe, CSI reporting method of the terminal.
In a terminal for transmitting channel state information (CSI: Channel State Information) in a wireless communication system,

An RF unit for transmitting and receiving radio signals; And

A processor controlling the RF unit; Including,

The processor,

Receiving from the base station CSI-RS resource information about a CSI-RS resource to which channel state information-reference signal (CSI-RS) is mapped;

Receive the CSI-RS from the base station using at least one antenna port based on the received CSI-RS resource information,

Report the CSI generated based on the received CSI-RS to the base station,

The CSI-RS resource is configured by aggregating a plurality of legacy CSI-RS resources.